DRSD Casebacks

.. I have only seen three types of caseback on MOST regular production Double Reds...

The regular production one with "Rolex" across the back...as the picture
above...

or the early production "patent pending" as below..

The second caseback is below.

Inside the caseback, the FULL serial number or last 3 of the serial should be
engraved along with the model number (1665) which of course should match the
case serial.

The last caseback is the
rounded type.. Now, I know what you are saying. DRSD did not have a
rounded type of caseback. Well, contrary to some of the mainstream
knowledge, some correct DRSD were born with a caseback usually
associated with White SD. The reason we know that they are correct is
that they were purchased from the original owners in that condition and
secondly all had the full serial number engraved inside the caseback (as
high as 5.2 mil). So yes, the rounded caseback is a DRSD caseback.